Maintains connections and is responsible for controlling ports and sessions. See OSI model, Open Systems Interconnection model. Related terms Physical Layer, Layer 1 Transmits raw bit stream over physical medium Application Layer, Layer 7 Human-computer interaction layer, where applications can access network services. See our API Security Platform in action Experience the speed, scale, and security that only Noname can provide. You'll never look at APIs the same way again. Book a Demo